feat(bot): доступ по QR-приглашениям, раздел «Участники», отзыв доступа

- AccessService: одноразовые приглашения (128 бит, в БД только sha256, TTL 24 ч),
  атомарный захват приглашения (условный UPDATE — из двух сканов одного QR проходит один),
  антиперебор (> 5 неудач в час — молчание), отзыв (черновик и FSM удаляются), повторное приглашение
- ADMIN_IDS заводятся в БД при старте; дальше — только по приглашению
- AccessMiddleware: участники из БД (+ last_seen раз в 5 мин), новичкам — только /start <токен>
- «👥 Участники» для админов: список, QR (segno) + ссылка, отзыв с подтверждением
- один ответ на неверный/истёкший/использованный токен — без подсказок

Refs #25

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/bot/routers/common.py

@@ -1,15 +1,18 @@
-"""/start, /help, /menu, main menu buttons and in-section navigation."""
+"""/start (incl. invite deep links), /help, /menu, main menu buttons and in-section navigation."""
 
 from aiogram import F, Router
-from aiogram.filters import Command, CommandStart
+from aiogram.filters import Command, CommandObject, CommandStart
 from aiogram.fsm.context import FSMContext
 from aiogram.types import CallbackQuery, Message
 
+from app.access.service import AccessService, RedeemStatus
 from app.bot.menu import Nav, NavAction, Section, main_menu, section_by_button, section_nav
+from app.bot.middlewares.access import tg_user
+from app.db.models import Role, User
 from app.texts import Texts
 
 
-def build_router(texts: Texts, admin_ids: frozenset[int]) -> Router:
+def build_router(texts: Texts, access: AccessService) -> Router:
     router = Router(name="common")
     sections = section_by_button(texts)
     section_text = {
@@ -17,33 +20,39 @@ def build_router(texts: Texts, admin_ids: frozenset[int]) -> Router:
         Section.STATUS: texts.section.status,
         Section.LOGS: texts.section.logs,
         Section.ALERTS: texts.section.alerts,
-        Section.MEMBERS: texts.section.members,
     }
 
-    def is_admin(message: Message) -> bool:
-        return message.from_user is not None and message.from_user.id in admin_ids
-
     @router.message(CommandStart())
-    async def start(message: Message, state: FSMContext) -> None:
+    async def start(message: Message, command: CommandObject, state: FSMContext, member: User | None) -> None:
+        if member is None:
+            # Only an outsider with an invite token gets here (AccessMiddleware); a member's /start <x> is a plain start
+            if message.from_user is None or not command.args:
+                return
+            status = await access.redeem(command.args, tg_user(message.from_user))
+            if status is RedeemStatus.THROTTLED:
+                return  # brute force: stay silent (SPEC A-6)
+            if status is RedeemStatus.REJECTED:
+                await message.answer(texts.start.invite_rejected)
+                return
+            member = await access.get_member(message.from_user.id)
+            if member is None:
+                return
         await state.clear()
-        await message.answer(texts.start.welcome, reply_markup=main_menu(texts, is_admin=is_admin(message)))
+        await message.answer(texts.start.welcome, reply_markup=main_menu(texts, is_admin=member.role is Role.ADMIN))
 
     @router.message(Command("menu"))
-    async def menu(message: Message, state: FSMContext) -> None:
+    async def menu(message: Message, state: FSMContext, member: User) -> None:
         await state.clear()
-        await message.answer(texts.menu.placeholder, reply_markup=main_menu(texts, is_admin=is_admin(message)))
+        await message.answer(texts.menu.placeholder, reply_markup=main_menu(texts, is_admin=member.role is Role.ADMIN))
 
     @router.message(Command("help"))
     async def help_(message: Message) -> None:
         await message.answer(texts.help.text)
 
-    @router.message(F.text.in_(sections))
+    @router.message(F.text.in_({k for k, v in sections.items() if v is not Section.MEMBERS}))
     async def open_section(message: Message, state: FSMContext) -> None:
-        section = sections[message.text or ""]
-        if section is Section.MEMBERS and not is_admin(message):
-            return
         await state.clear()
-        await message.answer(section_text[section], reply_markup=section_nav(texts))
+        await message.answer(section_text[sections[message.text or ""]], reply_markup=section_nav(texts))
 
     @router.callback_query(Nav.filter())
     async def navigate(query: CallbackQuery, callback_data: Nav, state: FSMContext) -> None: